Satellite and other spacecraft often carry components, such as optical payloads, sensitive to vibratory forces generated by reaction wheels, control moment gyroscopes, or other vibration-emitting devices aboard the spacecraft. Isolation systems are utilized to minimize the transmission of vibratory forces, especially high frequency vibratory forces commonly referred to as “jitter,” to such vibration-sensitive components aboard spacecraft. A precision isolation system may combine a certain number of individual isolators (typically three to eight isolators) to provide high fidelity damping in six degrees of freedom. In the case of passive isolation system, viscoelastic isolators (e.g., multi-directional rubber mounts) are often utilized. Viscoelastic isolators are relatively simple, low cost, lightweight devices, which typically provide damping along three orthogonal axes and, thus, in three degrees of freedom. However, the damping characteristics of viscoelastic isolators are non-linear and can vary significantly with changes in amplitude, displacement, and temperature. The damping characteristics of isolation systems incorporating viscoelastic isolators consequently tend to be somewhat limited and difficult to accurately predict.
Viscoelastic isolators are considered two parameter devices, which behave mechanically as a damper and spring in parallel. Advantageously, the peak transmissibility of a two parameter isolator is significantly less than that of an undamped device or a spring in isolation. However, after peak frequency has been surpassed, the damping profile of a two parameter device tends to decrease in gain at an undesirably slow rate. As a result, two parameter devices provide less than ideal attenuation of higher frequency vibrations, such as jitter. To overcome this limitation, three parameter isolators have been developed that further incorporate a second spring element in series with the damper and in parallel with the first spring element. The addition of the second spring in series with the damper allows a more precipitous decrease in gain with increasing frequency after peak frequency has been reached. As a result, three parameter isolators are able to provide superior damping characteristics at higher frequencies while maintaining relatively low peak transmissibilities. Three parameter isolators are thus able to provide superior damping of high frequency vibratory forces. An example of such a three parameter isolator is the D-STRUT® isolator developed and commercially marketed by Honeywell, Inc., currently headquartered in Morristown, N.J.
While providing the above-described advantages, three parameter isolators have traditionally been limited to damping in a single degree of freedom, namely, in an axial direction. At least six three parameter isolators are consequently required to produce a precision isolation system capable of high fidelity isolation in six degrees of freedom (“6-DOF”). By comparison, a 6-DOF isolation system can be produced utilizing as few as three multidirectional viscoelastic mounts combined in, for example, a three point kinematic mounting arrangement. Thus, relative to isolation systems employing multidirectional viscoelastic isolators, isolation systems employing three parameter, axial isolators have a high isolator count and, therefore, tend to be more complex, weighty, bulky, and costly to produce.
It would thus be desirable to provide embodiments of a three parameter isolator that provides damping in multiple degrees of freedom and, specifically, along three substantially orthogonal axes. Ideally, embodiments of such a three parameter, multi-axis isolator would provide a substantially linear damping profile over a relatively wide range in temperature, dynamic environment, and/or loading conditions. It would also be desirable to provide embodiments of an isolation system incorporating a plurality of three parameter, multi-axis isolators to provide, for example, high fidelity isolation in six degrees of freedom. Finally, it would further be desirable to provide embodiments of a method for producing such a three parameter, multi-axis isolator. Other desirable features and characteristics of embodiments of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying drawings and the foregoing Background.